Comparative study of ZnO and TiO2 nanoparticles: physicochemical characterisation and toxicological effects on human colon carcinoma cells

The aim of the present study is to evaluate the toxicological effects such as cytotoxicity, oxidative stress and inflammation induced by zinc oxide nanoparticles (ZnO NPs) and titanium dioxide nanoparticles (TiO2 NPs) on Caco-2 cells. Neutral Red assay and Colony Forming Efficiency assay were performed after treatment with selected NPs concentrations in presence or in absence of foetal calf serum (FCS). Our results showed a significant dose and time dependent effect after treatment with ZnO NPs. The presence of FCS strongly reduced ZnO NPs toxic effect, probably through its interaction with the NPs surface. On the contrary, no effect was observed on Caco- 2 cells exposed to TiO2 NPs. Moreover, higher cell interaction was observed in cell exposed to ZnO and TiO2 NPs in serum-free culture medium than in complete cell culture medium. Level of intracellular reactive oxygen species (ROS), measured by 2,7-dichlorofluorescein diacetate (DCFDA) dye, increased in Caco-2 cells after 6 and 24 h of ZnO NPs treatment. TiO2 NPs induced higher ROS production in a dose dependent manner after 6 h. Moreover exposure to ZnO NPs induced IL-8 release, an important chemokine for innate immune response and recruitment of acute inflammatory cells. The influence of physical and chemical properties of ZnO NPs and TiO2 NPs on observed biological effects was also discussed. The characterization of particles was carried out by dynamic light scattering (DLS), electron microscopy (SEM, TEM) and inductively coupled plasma-mass spectrometry (ICP-MS). Our results suggest a key role of oxidative stress in ZnO NPs cytotoxicity induction related to ion leakage and to cell interaction with NPs in serum free medium.JRC.I.4-Nanobioscience